Sometimes Frame Size sticks in Reality. That happens most (to me, at any rate) after using Perfect Shot. Even in a new scene, the Frame Size is frozen at 720 x 1280.

That isn't the fault of Reality.

It's Iray!

Iray sees that as a custom frame size, and memorizes it. Being the not-nearly-as-smart-as-Paolo program that it is, Iray applies the memorized size to the next scene, whether we want it to, or not. We have to manually change the setting in Iray to unfreeze Reality.

In the DAZ Setup screen, go to Render. Select the second option, Render Settings. This brings up the Iray render panel. Select the first option, General. The very first option is Dimension Preset (Global). That is Iray's frame size. See what it says. If Custom is checked, that's your culprit. Change it to Active Viewport. That will unfreeze the Frame Size in Reality.